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Types of Muscles
Striated (skeletal): banding pattern due to
arrangement of fibres, voluntary function,
scattered nuclei and involved in movement.
Smooth (involuntary): found in the
digestive/reproductive system, iris and in
blood vessels which contract and fatigue
slowly.
Cardiac (involuntary): found in the heart,
striated but has cross bridges, myogenic,
random nuclei, contracts spontaneously
and never tires.…read more

Slide 3

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Structure of Skeletal Muscle
There are several sarcomeres in one myofibril which
forms a muscle fibre, a bundle of these creates a
muscle.
I band = light
A band = dark…read more

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Myosin and Actin
Thick filament Thin filament
2 long polypeptide 2 chains of
chains twisted around monomers (troponin
each other and tropomyosin)
Globular head with Myosin binding sites
ADP and Pi attached
Tropomyosin Troponin Actin
Myosin…read more

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Muscle Contraction ­ Sliding Filament
Theory
Innovation: the action potential depolarises
the neurone, impulse travels to motor end
plate (effector).
Sarcoplasmic reticulum releases calcium
ions by exocytosis in triad of vesicles and
binds to troponin.
Troponin changes shape pulling the
attached tropomyosin out of the actin-
myosin site on actin.
Myosin head attaches to/twists/pulls the
binding site shortening the sarcomere
(ratchet mechanism).…read more

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Importance of ATP in Contraction
ATP provides the energy needed to move
the myosin head and to break the
actomyosin cross bridge.
Calcium activates the enzyme ATPase
which is involved in ATP production.
The cycle is repeated as long as calcium
and ATP are present.…read more

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